1. Field of the Invention
The present invention relates to tools for imparting torque to a workpiece and, more particularly, to a flex-head wrench having a handle which is pivotable orthogonally with respect to the plane of the tool head and an improved locking feature for selectively locking the pivoting handle in place.
2. Description of the Background
Many different wrenches have been developed each with specialized feature(s) adapted for particular working conditions.
One such condition frequently arises in a crowded or enclosed environment. In this situation, the turning arc of the wrench may be blocked or limited by neighboring objects or structures. A variety of flex-head wrenches has been developed which overcomes this problem by allowing an operator to adjust the angular position of the handle orthogonally with respect to the plane of tool head. This way, the operator can maneuver the wrench handle around the obstruction.
In its simplest form, a flex-head wrench includes a handle portion joined to a tool-head at a pivot joint. If the turning arc of the handle becomes obstructed, the operator simply adjusts the angle of the handle. This way, most obstructions can be avoided without removing the tool head from the workpiece. Unfortunately, control of the handle is easily lost when high torque is applied, and the handle has a tendency to change position. This may injure the operator.
Certain flex head wrenches provide an additional feature by which the handle may be locked in a desired angular position with respect to the plane of the tool head. The locking feature helps to maintain control of the wrench even when high torque is being applied. The locking feature is also useful when fitting the wrench socket onto a nut or bolt.
As an example, U.S. Pat. No. 4,581,959 discloses a locking flex-head which pivots orthogonally to the plane of the wrench head. A yoked handle is shown carrying a pivotably mounted tool head. A parallelepiped is integrally formed rearwardly of the tool head, and the parallelepiped is carried axially by the yoked handle. Each face of the parallelepiped is defined by a transverse notch. A spring-mounted detent pin extends from the handle and engages the notches on the parallelepiped faces. The tool head can be locked in one of six incremental angular positions with respect to the handle by engaging the spring-mounted detent in the respective notch.
Although the '959 patent accomplishes the basic function of a locking flex head tool, in so doing it creates other problems. For example, the tool head with integral parallelepiped is exceedingly difficult and costly to manufacture. In addition, the full measure of torque at the parallelepiped is imparted on the detent pin. This creates a highly focussed stress point which leads to breakage of the detent pin and/or deterioration of the notches. Furthermore, it is difficult to securely lock the parallelepiped in position. To secure the locking means an adjustment knob must be turned to the tightest possible position. It would be far more advantageous if the basic locking flex head function could be accomplished with a simpler, stronger, and more economical design.
More preferable alternatives are shown in U.S. Pat. Nos. 4,901,608 and 4,711,145. Both patents illustrate adjustable angle ratchet wrenches having a tool head pivoted at a hub which has rearwardly protruding teeth. An opposing mechanism mounted in the handle may be moved into engagement with the toothed hub to lock the tool head in place. However, the mechanisms taught for engaging the teeth of the tool head are intricate, exceedingly difficult and costly to manufacture. For instance, five finely machined parts are necessary in the '608 patent (see FIG. 1, refs. 3-6 and 211), and two drill passes must be made through the handle. The manufacturing difficulties are even more apparent in the '145 patent, where an intricate lengthwise borehole must be made through the handle.
It is questionable whether the above-described patents or any other prior art references teach a commercially practical wrench. This is evidenced by the unavailability of any commercial unit incorporating a comparable locking mechanism.
It would be greatly advantageous to provide a flex-head locking mechanism incorporating a minimum of easily manufacturable parts. This would increase the strength and durability of the wrench while reducing manufacturing costs.